1. Field of the Invention
The present invention relates to semi-conductor manufacturing equipment and more particularly a method and apparatus for providing instructions to process tools.
2. Description of Related Art
Semiconductor manufacturing involves various steps such as adding material to a layer, removing material from a layer or modifying a layer of a substrate. Material may be added, removed, and/or modified selectively or in bulk. The steps may result in modifying physical properties of the layers, such as thickness of the layer, index of refraction of the layer, coefficient of absorption of the layer etc., which may affect the performance of the semiconductor. Thus, it is useful to measure and control the properties of the various layers.
One method of measuring the properties is to cut (e.g., scribe and break) the substrate through a feature of interest, thus exposing a cross-section of the feature. The feature may then be examined using microscopy, for example, scanning electron microscopy (SEM). Unfortunately, the substrate is generally destroyed by cutting. Moreover, the number of features that can be examined may be limited to features lying along the cut.
Another method includes creating a proxy in the form of features that are intended to be representative of one or more dies. The proxies may be placed between selected dies on the substrate. The features in the proxy may be measured during various steps in the manufacturing process using a probe in the form of a light beam having small spot size about the size of the proxy structure. However, it can be difficult to align the substrate and position the proxies within such a small spot size. Unfortunately, features in the proxies may not be representative of features in the dies.
Other methods of measuring properties of layers of a substrate include using SEM review and/or metrology tools that do not involve destroying the substrate. However, the SEM beam may burn areas of the substrate, and alignment of the small SEM beam may be difficult and/or time consuming. What is needed is an improved apparatus and method for measuring properties of a substrate to allow instructions to be sent to the process tools during operations or for future operations.